docs: def encode_kv_node(keypath, child_node_hash):
      """
      Serializes a key/value node
      """
      if keypath is None or keypath == b'':
          raise ValidationError("Key path can not be empty")
      validate_is_bytes(keypath)
      validate_is_bytes(child_node_hash)
      validate_length(child_node_hash, 32)
      return KV_TYPE_PREFIX + encode_from_bin_keypath(keypath) + child_node_hash